Our objective is to develop a photochemical method (PCD) to inactivate infectious pathogens (bacteria, viruses, protozoa) in human blood products. Methodology using the novel psoralen S-59 and long wavelength ultraviolet a light ( 320-400 nm) has been developed which inactivated pathogenic bacteria and viruses in human platelet concentrates (pc), leaving in vitro human platelet function intact. In vivo murine transfusion model studies have confirmed that post transfusion recovery and survival of pcd treated murine platelets are normal. Primate research focuses on using non-human primate models to examine effects of pcd treatment on post transfusion recovery and survival of macaque platelets. This model serves as the final step prior to human studies. Macaque platelets and red cells are labeled with a fluorescent probe. A process has been developed to prepare pc from macaque whole blood under the same conditions used to prepare human pc for transfusion support of human patients. The pcd process has no significant effect on macaque platelets as measured by in vitro assays. Using these methods, total blood volume and post transfusion recovery and survival of autologous platelets have been measured in a series of control animals. No adverse effects have been observed in transfused animals nor on post-transfusion recovery and survival. In a second study, human platelets treated with s-59 pcd were infused into macaques for 7 days to look for adverse effects. None were observed. This information will be used to design a larger safety study to evaluate adverse effects of s-59 treated platelets on primates. The macaque platelet transfusion model will provide critical information about effects of the pcd process on primate platelets prior to human clinical studies. Following platelet transfusion studies, similar studies will be carried out using another photochemical process designed to decontaminate red blood cells.